An integrated coating system has been disclosed in U.S. patent application Ser. No. 12/026,724, which is incorporated herein by reference to the extent necessary to understand and/or practice the water heating apparatus claimed in the present patent application. This integrated coating system is developed to produce reliable high temperature heating elements capable of performing reliable and consistent heating functions up to about 600° C. The coating system is deposited on a flat ceramic glass substrate and includes multi-layers of conductive coatings of nano-thickness of proprietary base chemistry, doped elements and process conditions, with capacity to maintain stable structure and performance at high temperature heating. The coating system further includes specially formulated ceramic frit parallel electrodes formed across the coatings to ensure optimum matching between the electrodes and the coatings and the substrate in reducing electric resistance and improving conductivity across the heating element. The coating system can be manufactured using spray pyrolysis at controlled temperature between about 650° C.-about 750° C. and controlled spray movement in formation of multi-layered nano-thickness films of about 50 nm-about 70 nm leading to increased stability at high temperatures.
A conductive coating material is used to convert electric power into heat energy. The heat generation principle as used is very different from conventional coil heating in which heating outputs come from the resistance of the metal coils with low heating efficiency and high power loss. In contrast, by adjusting the composition and thickness of the layers of coating, electric resistance of the coating system can be controlled and conductivity can be increased to generate high efficiency heating with minimal energy loss. An integrated coating system has been developed to produce reliable high temperature heating elements capable of performing reliable and consistent heating functions up to about 600° C. An intelligent power monitor and control system using analog-to-digital converter (ADC) and pulse-width modulation (PWM) drives integrated with the heating films can be provided in smoothing the power supply to the heating elements and optimizing their heating performance and energy saving efficiency in accordance with the required water temperature and flow rate.
The above description of the background is provided to aid in understanding a water heating apparatus, but is not admitted to describe or constitute pertinent prior art to the water heating apparatus disclosed in the present application, or consider any cited documents as material to the patentability of the claims of the present application.